This study is directed at vaccine challenge of feline patients to FIV/listeria lysin fusion proteins as a model for development of human HIV recombinant vaccine. Lenti viruses, when passed in cell culture, tend to become attenuated and may stop mutating. Mutation is a major obstacle in developing an effective FIV vaccine. This renders many prototype vaccines useless in the prevention of disease. FIV and HIV are not only structurally similar but present the researcher challenges in the arena of vaccine development due to their propensity to mutate in the wild state. Phase I of our study will be to characterize an infective dose of FIV in healthy felids which describes a subclinical illness but in which viral organisms naturally mutate. Phase II will be to harvest serum from these animals and to isolate proteins from the viral coat GAG, POL, and REV; to fuse these proteins in the laboratory with lysterialysin protein. This will form the basis for a vaccine challenge in which the lysterialysin will result in cytokine-mediated humoral and cellular immunity. We hypothesize that this vaccine will initiate a memory of immune comments to multiple mutations of the viral coat. The study is currently in the first third of Phase I.